CN103121105A - Method for preparing micro spherical niobium (Nb)-wolfram (W)-molybdenum (Mo)-zirconium (Zr) alloy powder - Google Patents

Abstract

The invention belongs to the field of powder materials and particularly provides a method for preparing micro spherical niobium (Nb)-wolfram (W)-molybdenum (Mo)-zirconium (Zr) alloy powder. According to the method, the mechanical alloying technology is used for preparing Nb-W-Mo-Zr alloy powder, and then the radio frequency plasma spheroidization technology is used for treating the mechanical alloying alloy powder to obtain the micro spherical Nb-W-Mo-Zr alloy powder which is suitable for being used for manufacturing micro thin-wall parts in an injection forming mode, wherein the average particle diameter of the micro spherical Nb-W-Mo-Zr alloy powder is less than 20 micro meters. The method for preparing the micro spherical Nb-W-Mo-Zr alloy powder overcomes the defect that through a traditional niobium alloy powder preparation technology, only powder with particles which are in irregular shapes or have long diameters can be prepared, the average particle diameter of the prepared micro spherical Nb-W-Mo-Zr alloy powder is less than 20 micro meters, and the prepared micro spherical Nb-W-Mo-Zr alloy powder is high in degree of sphericity and good in flowability, is quite suitable for being used for manufacturing thin-wall Nb-W-Mo-Zr alloy parts in a powder metallurgy mode, is especially suitable for being used for manufacturing the thin-wall Nb-W-Mo-Zr alloy parts in the injection forming mode.

Description

A kind of method for preparing minute spherical Nb-W-Mo-Zr alloy powder

Technical field

The invention belongs to the metal dust research field, a kind of method for preparing minute spherical Nb-W-Mo-Zr alloy powder is provided especially.

Background technology

Owing to having excellent mechanical behavior under high temperature and special physical and chemical performance, niobium-base alloy is widely used in aerospace, atomic energy and superconduction field, is considered to the most promising structural material of using in can the hot environment more than 1500K.The main flow niobium alloy structural material that the Nb-W-Mo-Zr alloy is used as China's Aero-Space is widely used in making the parts such as rocket motor injector, rocket tail.

At present, most niobium alloys are all to adopt the traditional handicraft preparation, comprise numerous operations such as melting, casting, pressure processing, welding, exist stock utilization low, pollute large, be difficult to prepare the deficiency such as Irregular Shaped Parts.Especially only there are 10-30mm, wall thickness that several mm are only arranged for manufacturing dimension and with the tiny niobium alloy parts of the labyrinths such as blind hole, step, groove, circular arc, the preparation difficulty of traditional diamond-making technique is very large.As emerging PM technique, metal powder injection molded (MIM) can the near-net-shape metallic element, especially be fit to small, the baroque fine parts of manufacturing dimension in enormous quantities, be widely used in the parts manufacturing of the material systems such as titanium alloy, stainless steel, iron-based, high density, carbide alloy at present.Due to the restriction that is subject to the alloy powder production technology, the correlative study of MIM niobium alloy is all rarely found both at home and abroad.

Metal powder injection molded technology has specific (special) requirements to indexs such as the shape of powder, granularity, mobility.Good sphericity, suitable powder size, high mobility are the keys of the high-quality injection moulding feeding of preparation, can improve the feeding useful load, guarantee the isotropism of injection base and the even contraction in sintering process, thereby reduce part deformation, assurance dimensional accuracy.In general, the metal dust that the most suitable injection moulding is used should be the spherical powder of 20 left and right, and for the complicated especially thin-walled parts of preparation structure, the particle diameter of powder needs more tiny.

And due to the fusing point of niobium high (2460 ℃), active large (easily with reactions such as alloying element, clearance-type atomic carbon, oxygen, nitrogen), the preparation of niobium alloy powder is a large technical bottleneck of restriction powder metallurgy niobium alloy production always.At present the niobium alloy powder preparation method of higher degree mainly contains hydrogenation-go hydrogenization method, ion rotary electrode method, electron beam atomization, electron beam rapid solidification and mechanical alloying method.And with this several method production, separately shortcoming is arranged, and be not suitable for producing niobium alloy injection moulding powder, especially be not suitable for producing granularity that part small for the preparation of size, that have thin-wall construction uses at the spherical niobium alloy powder below 20 microns.

Hydrogenation-dehydrogenation method is that the differences of mechanical properties of utilizing niobium to inhale after hydrogen, dehydrogenation prepares powder, mainly comprises hydrogenation, powder process and three steps of dehydrogenation.At first be the hydrogenation of niobium alloy, after element powders is smelted into the niobium alloy ingot casting, is divided into fritter high-temperature heating under hydrogen atmosphere and oozes hydrogen, then be cooled to room temperature.Next is powder process, utilizes fragmentation, efflorescence equipment that the block hydrogenated niobium that diameter is not more than 2.5cm is carried out fragmentation, classification under inert gas shielding, prepares the niobium alloy powder of hydrogenation.Be dehydrogenation at last, under cryogenic conditions, with niobium alloy powder Repeat-heating dehydrogenation in vacuum drying oven of hydrogenation, obtain the in irregular shape niobium alloy powder identical with original niobium alloy ingot casting microstructure.The niobium powder out-of-shape of the method preparation, poor fluidity is unsuitable for preparing powdered metal parts, but can utilize its excellent superconductivity to prepare superconductor.

Electron beam atomization technique is the unique industrialization means of high-purity refractory metal that obtain at present.Its principle is, under vacuum condition, the niobium ingot via the VAR melting in the EB chamber moves under electron gun, and high-power electron beam makes its continuous fusing, and drip melt is on atwirl water-cooled copper dish, and molten drop is cast aside by rotating disc.Drop is because capillary effect is spherical in shape, with the collision of chamber wall in be cooled to rapidly alloy powder.Except vacuum condition, niobium alloy powder also can prepare under helium or argon gas atmosphere.The niobium alloy powder gap field trash of the method preparation is less, and purity is higher, but production cost is high, powder diameter thick (average grain diameter is at 350 μ m), is not suitable for preparing injection moulding niobium alloy part small, thin-walled.

The operation principle of PREP method is that the niobium alloy ingot casting is processed into bar-shaped consutrode, the electrode bar end face of High Rotation Speed is melted by plasma arc, the drop that is melted on bar end face flies out under the effect of centrifugal force, is rapidly solidificated into spherical powder particle in cooling medium (vacuum, helium or argon gas).The average grain diameter of the powder of the method preparation also about 150 μ m, also is not suitable for preparing injection moulding niobium alloy part small, thin-walled.

The electron beam rapid solidification method is that the electron beam centrifugal atomization apparatus is improved a little, and the atomized flow of alloy liquid droplet is directly struck on a water-cooled copper plate, obtains the preparation method of the sheet alloy powder of rapid solidification.Adopt the sheet niobium alloy powder of the method preparation, have in the zone, interdendritic than EBA, cooldown rate that the PREP powder is larger, the alloy liquid droplet state of these pine-tree structures before rapid solidification be forming core just.The niobium alloy powder of the method preparation in the form of sheets, poor fluidity is not suitable for injection moulding use, can be used for the fields such as plasma spraying.

Mechanical alloying method is that element powders that proportioning is good and abrading-ball are placed in the ball grinder that is full of inert gas and carry out high-energy ball milling.Utilize abrading-ball to powder clash force to input energy, make between powder the processes such as constantly repeated deformation, cold welding, fragmentation, promote the diffusion between element, the formation alloy powder.Although the powder size that the method is produced is tiny, shape is not spherical, and poor fluidity is not suitable for preparing that injection moulding is fine, thin-walled parts yet.

Radio frequency plasma (RF) body spheronization techniques, that powder particle in irregular shape is sprayed in plasma torch by feeding gun by carrying gas, fusing rapidly in the hot environment of plasma torch, the particle of melting forms the very high drop of sphericity under surface tension effects, and solidify rapidly, thereby obtain tiny spherical powder under high thermograde.

Summary of the invention

The purpose of this invention is to provide a kind of method that can be used for preparing minute spherical Nb-W-Mo-Zr alloy powder.The Nb-W-Mo-Zr alloy powder sphericity of the method preparation is high, powder diameter is little, can be used for especially being fit to the Nb-W-Mo-Zr alloy part that preparation size is small, have thin-wall construction in powder injection forming production.

The present invention adopts the method for mechanical alloying to prepare the Nb-W-Mo-Zr alloy powder, then adopt the radio frequency plasma spheronization techniques that the mechanical alloying powder is processed, to obtain be fit to making average grain diameter that injection moulding small, thin-walled parts uses at the Nb-W-Mo-Zr alloy powder below 20 microns.The technological process of the method is as shown in Figure 1:

At first, press the required element powders of element proportioning weighing;

Secondly, with element powders ball milling in high-purity argon gas or vacuum atmosphere, drum's speed of rotation is controlled in the scope of 200-500r/min, and Ball-milling Time is 20-70h;

The axle powder such as Fig. 2 and Fig. 3 are the SEM photos before and after Mechanical Alloying, and as can be seen from the figure, granularity differs, different element powders becomes homogeneous after ball milling, tiny.

Further, the powder that ball milling is obtained carries out the radio frequency plasma spheroidising, by adjust plant capacity between 65-75KW, feed rate at 4-8g/min, system pressure between 97-100 KPa, carrier gas flux between 1.5-2.5 L/min, the central gas flow between 2-3 L/min, the limit throughput is controlled its nodularization effect between 85-95 L/min;

Fig. 4 and Fig. 5 are respectively SEM photo and the XRD diffraction patterns of nodularization powder, and as can be seen from the figure, the nodularization powder has been realized alloying, the good sphericity of powder, and the nodularization rate is high, and powder is tiny, and most powder diameters are below 20 μ m;

At last, the nodularization powder is detected, packs, seals.

Advantage of the present invention is that the Nb-W-Mo-Zr niobium alloy powder of preparation is tiny, average powder diameter below 20 μ m, high, the good fluidity of sphericity, in the time of can satisfying injection molding process and produce small, thin-walled niobium alloy parts to the requirement of powder.

Description of drawings

Fig. 1 is process chart of the present invention

Fig. 2 is the element powders of processing without mechanical alloying

Fig. 3 is the powder after mechanical alloying is processed

Fig. 4 is the powder after the radio frequency plasma spheroidising

Fig. 5 is the XRD diffraction pattern of powder after the radio frequency plasma spheroidising

The specific embodiment

Embodiment 1: adopt the present invention to prepare minute spherical Nb-5wt% W-2wt% Mo-1wt% Zr alloy powder

Adopting purity＞99.8%, granularity is the Nb powder of-325 mesh; Purity＞99.9%, granularity are the W powder of 3-5 μ m; Purity＞99.9%, granularity are the Mo powder of 1-2 μ m; Purity＞99.5%, granularity are that the Zr powder of 4-8 μ m is raw material;

Be that Nb-5wt%W-2wt%Mo-1wt%Zr carries out weighing and joins powder according to alloying component;

The powder that configures is carried out mechanical alloying on planetary ball mill, rotational speed of ball-mill is 400r/min, and Ball-milling Time is 50h;

Powder after mechanical alloying is carried out the radio frequency plasma spheroidising, and plant capacity is that 70 KW, feed rate are that 6 g/min, system pressure are 99 KPa, and carrier gas, central gas and limit throughput are respectively 2 L/min, 2.5 L/min and 90 L/min;

Powder after plasma spheroidization is detected, packs, seals, and the sphericity of powder reaches more than 97%, and the nodularization rate is on 98%, and the largest particles diameter is no more than 25 μ m, and average grain diameter is 15 μ m.

Claims (2)

1. the preparation method of the minute spherical Nb-W-Mo-Zr alloy powder of an average grain diameter below 20 μ m is characterized in that the method comprises the following steps:

At first, press the required element powders of element proportioning weighing;

Secondly, with element powders ball milling in high-purity argon gas or vacuum atmosphere, drum's speed of rotation is controlled in the scope of 200-500r/min, and Ball-milling Time is 20-70h;

Further, the powder that ball milling is obtained carries out the radio frequency plasma spheroidising, by adjust plant capacity between 65-75KW, feed rate at 4-8g/min, system pressure between 97-100 KPa, carrier gas flux between 1.5-2.5 L/min, the central gas flow between 2-3 L/min, the limit throughput is controlled its nodularization effect between 85-95 L/min;

At last, the nodularization powder is detected, packs, seals.

2. the preparation method of minute spherical Nb-5wt% W-2wt% Mo-1wt% Zr alloy powder as claimed in claim 1 is characterized in that the method is specially:

Adopting purity＞99.8%, granularity is the Nb powder of-325 mesh; Purity＞99.9%, granularity are the W powder of 3-5 μ m; Purity＞99.9%, granularity are the Mo powder of 1-2 μ m; Purity＞99.5%, granularity are that the Zr powder of 4-8 μ m is raw material;

Be that Nb-5wt%W-2wt%Mo-1wt%Zr carries out weighing and joins powder according to alloying component;

The powder that configures is carried out mechanical alloying on planetary ball mill, rotational speed of ball-mill is 400r/min, and Ball-milling Time is 50h;

Powder after mechanical alloying is carried out the radio frequency plasma spheroidising, and plant capacity is that 70 KW, feed rate are that 6 g/min, system pressure are 99 KPa, and carrier gas, central gas and limit throughput are respectively 2 L/min, 2.5 L/min and 90 L/min;

Powder after plasma spheroidization is detected, packs, seals.

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